System for locating a radiatedsignal reflector



H. M. LEWIS Filed Oct, 27, 1943 BAND-PASS SELECTORSJMODULAORS Aug. 26, 1947.

SYSTEM FOR LOCATING A RADIATED-SIGNAL REFLEcToR F'GI A INVENToR HAROLD M. Lswls 'BY i ATroNEY la 12b Aug. 26,1947.

Filed oct. 27. 1946 3 Sheets-Sheet 2 BAND-PASS HAROLD M. LEWIS ugZ, 1947- H. M. I Ewls 2,426560 SYSTEM FOR LOCATING A RADIATED-SIGNAL REFLEGTOR Filed oct. 27, 194s s sheets-Sheet 3 BAND-PASS INVENTOR HAROL M; LEWIS I ,8% V

ATTZRNEY Patented Aug. 26, 1947 SYSTE'BI FOR LOCATING A 'RADIATED- SIGNAL REFLECTOR Harold M. Lewis, Allenhurst, N. J., assigner, by mesne assignments, .to Hazeltine Research, nc., Chicago, Ill., a corporation of Illinois Application October 27, 1943, Serial No. 507,861

The present invention relates to systems for locating a radiated-signal reilector. More particularly, the invention relates to such systems of the type in which a predetermined space is scanned with a sharply concentrated radiatedsignal beam and radiated-signal energy of the beam reflected by the reflector, which may for example be an aircraft, is utilized to pro-vide an indication of the direction and distance of the reflector from the system.

It has been proposed in aircraft locating systems that a predetermined space be scanned in either one or two directions with a sharply concentrated radiated beam of wave signals and that the wave-signal energy which i-s reflected from the aircraft be received and utilized to provide an indication of the direction and distance of the aircraft from the locating station. This has been accomplished in several prior art arrangements by the provision of a radiated-signal translator system having a radiation characteristic in the form of a sharply concentrated beam, this translator system being physically rotated by suitable mechanical apparatus to eect the scanning action. rihe general disadvantage and limitations of mechanical scanning arrangements of this nature are well understood by those skilled in the art. Among these may be mentioned the disadvantages that appreciable power is required physically to move the radiated-signal translating system for purposes of scanning and the fact that the rate of scanning is at best rather low which unduly restricts and limits the usefulness of the system.

A wave-signal scanning system substantially entirely electrical in nature forms the sub-ject matter of copending applications of Arthur V. Loughren, Serial Nos. 395,172 and 418,712, led May 26, 1941, and November 12, 1941, now Patents 2,407,169 and 2,409,944, issued September 3, 1946, and October 22, V1946, respectively. That system provides that the sharply directive response characteristic of the system be caused to scan a predetermined space by the use of an array of physically spaced radiated-signal translators which are coupled through individual Wave-signal delay means or Shifters to a common wave-signal translating channel. The present invention constitutes an improvement on the electrical scanning system of the aforesaid Loughren applications.

It is an object of the present invention, therefore, to provide a new `and improved system for rlocating a radiated-signal reflector which avoids 13 Claims. (Cl. Z50- 11) one or more of the disadvantages and limitations of the prior art Systems of this nature.

Itis a further object of the invention to provide a system for locating a radiated-signal reflector in which scanning of a predetermined space is effected entirely by electrical means which does not require any moving mechanical parts and one which involves a fundamental simpliiication and improvement of electrical phasing means employedv therein to accomplish the desired scanning action.

-It is an additional object of the invention to provide a system for locating a radiated-signal reflector in which a predetermined space is scanned with a radiated-signal beam and either or both the rate of scanning and the configuration of the scanning beam may be readily and easily controlled by one or more simple adjustments of wave-signal apparatus included in the system.

-It is a further object of the invention to provide a newV and improved system for locating a radiated-signal reflector and one which is exceptionally well adapted to the type of operation wherein pulse modulationv of wave-signal energy translated by the system is utilized to effect high power output relative to the average power capabilities of the apparatus utilized.

It is an additional object of the-invention to provide a new and improved system for locating a radiated-signal reflector in which the receiver component thereof has a sharply directive response characteristic which angularly scans a predetermined space in synchronism with the radiated-signal beam of the system but displaced at any selected angle with relation thereto.

In accordance with the invention, a system for locating a radiated-signal reflector comprises a radiated-signal translating system including a plurality of ,spaced signal translators and wavesignal ksupply means for applying wave signals to at least one of the translators and wave signals of a different frequency to another of the translators to provide a radiated-signal translating .system whichangularly scans a predetermined space with a radiated-signal beam. The .beam

`scans across any radiated-signal reector in the aforesaid space and radiated-signal energy of the beam is reflected therefrom. The system also includes modulator means for modulating the reected radiated-signalvenergy received by one of the .translators with a modulation signal having a predetermined frequency difference from the wave signal applied to the first-mentioned one 4translator and for modulating the yreflected radiated-signal energy received by another of the translators with a modulation signal having, with respect Ito the wave signal applied to` the aforesaid first-mentioned other translator, a predetermined frequency dierence such that predetermined ones of the resulting modulation components have additive phase only for one direction of reception by the last-mentioned translators, which direction scans the aforesaid predetermined space in synchronism with the radiatedsignal beam. The system additionally includes means for combining and utilizing the aforesaid predetermined modulation components to indicate the direction of the reflector from the system.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following descrip-- tion taken in connection with the accompanying drawings, and its` scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. 1 represents, schematically, a complete system for locating a radiated-signal reector embodying the present invention; Fig. 1A represents directive scanning patterns of the Fig. 1 system at two selected moments in a scanning cycle and is used as an aid in explaining the operation of the invention; Fig. 1B is an illustrative indication used in explanation with Fig. 1A; Fig. 1C represents selected portions of the radiated-signal translating system, per se, of the Fig. 1 arrangement and is used as an aid in explaining the operation of the locating system; Fig. 2 represents, schematically, a complete system which embodies the present invention in a modied form; Fig. 3 represents, schematically, a portion of a locating systemY which embodies the present invention in another modified form; and Fig. 4 illustrates the directive characteristic of this arrangement at three selected instants during a scanning cycle.

Referring now more particularly to Fig. 1 of the drawings, there is represented, schematically, a complete system for locating a radiated-signal reector which embodies the present invention in a particular form. This system includes a radiated-signal translating system I having a plurality of spaced signal translators |l-20, inclusive. These translators may, for example, be vertical dipole antennas horizontally aligned and preferably are grouped into two spaced translator arrays diie and b with the translators in each array linearly aligned. The translators of each of the arrays lila and I 0b preferably are equally spaced by values dependent upon the desired conguration of the major directivity lobe which is characteristic of such arrays.Y The mannerin which the spacing of the translators affects the major directivity lobeV is considered in detail in the copending application of Harold M. Lewis, Serial No. 507,859, filed concurrently herewith, entitled System for space scanning with a radiated wave-signal beam, and assigned to the same assignee as the present application. For most applicationsVit is preferable to space the translators in each array by one-half wave length of the mean or nominal frequency of the wave signals applied to the translators of the array Illa.

The locating system of the present invention also includes wave-signal lsupply means for applying wave signals to at least one of the translators of the translating system l0 and wave signals of a different frequency to another of the translators of the system to provide a radiatedsignal translating system which angularly scans a predetermined space with a radiated-signal beam. This means comprises a source or generator 2l of scanning-control signals having frequencyV components related to the number and physical spacing of the translators; the frequency components in particular have frequency values proportional to the spacings of the translators from at least one common reference point. In a locating system having ve equally-spaced translators in each array, for example, the scanning-control signal generator 2l provides a scanning-control signal having two frequency components fh and Zh which thus have values of frequency proportional to the physical spacings of the translators from the centrally positioned translator, considered as a Yreference point. It will be understood, of course, that the stated values of the frequency components and equal spacings of the translators are chosen for purposes of example only and that the use of additional translators or unequal spacings thereof requires that the scanning-control signal have additional frequency components or frequency com.- ponents with values other than those recited.

The wave-signal deriving means additionally comprises means responsive to the scanning-control signals of the generator 2l for deriving a plurality of wave signals of individual different frequencies. nal generator 22, for generating'a subcarrier wave signal having a frequency fe, and a balanced modulator 23 having an input circuit coupled to the output circuits of both of the generators 2l and 22. The output circuit of the modulator 23 is coupled to a unit 24 comprising a plurality of band-pass selectors and modulators 25-29, inclusive, having the selectors thereof preceding the modulators and individually tuned to select individual frequency components of the modulated wave signal developed inthe output circuit of the modulator 23. The frequency fe of the subcarrier wave signal of generator 22 preferably is sufciently low that these modulation-frequency components may be easily separated by the selective action of the selectors of unitV 24. ,Hence there is included means for heterodyning these selected modulation-frequency components to a higher frequency, suitable for radiation, comprising a heterodyne oscillator 3S which generates a heterodyne wave signal of frequency fo and which has anoutput circuit Vcoupled to an input circuit of each of the modulators ofV unit 2. A plurality of band-pass selector and amplier units 3h35, inclusive, have input circuits coupled tothe output circuits of the respective selector-modulator units 25-23, inelusive, of unit 24 and have output circuits coupled, to the respective translators l l-l5, inclusive, of the array Ilia. The selectors of the units 3l-35, inclusive, precede the amplifiers thereof and are tuned toselect, in this instance, the sum-frequency heterodyne components developed in the output circuits of the modulators of unit 2G. The amplifiers of the'latter units preferably have relative gains such that the wave signals applied tothe translators H-l5, inclusive, have equal amplitudes.

As previously mentioned, the radiated-signal beam ofY the array ma angularly scans apredetermined space. In doing so, the beam scans across any radiated-signal reflector in this space andY radiated-signal energy ofV the beam is reected fromrany such reflector.

The locating system includes modulator means This means comprises a wave-sigfor modulating the reflected radiated-signal energy received by one of the translators of the receiving array lb with a modulation signal having a predetermined frequency difference from the wave signal applied to a translator of the array lila and for modulating the reflected radiated-signal energy received by another of the translators of the array I b with a modulation signal having With respect to the Wave signal applied to another translator of the array me a frequency difference not less than the last-mentioned predetermined frequency difference. Predetermined ones of the resulting modulation components have additive phase for one direction of reception by the last-mentioned translators, which direction scans the aforementioned predetermined space in synchronism with the radiated-signal beam. The receiver translators last mentioned are shown by way of illustration as comprising the translator array ills.

The modulator means last mentioned comprises means responsive to the scanning-control signals of the generator El for providing the required modulation signals. More particularly, the modulator means comprises a balanced modulator 36 having an input circuit coupled through an adjustable phase shifter 31 to the output circuit of the generator 2l and having an input circuit also coupled to the output circuit of the Wave-signal generator 22. The output circuit of the modulator 3S is coupled to the input circuit of a unit 3B which includes a plurality of bandpass selector and modulator units 39-43, inclusive, the selectors of which precede the modulators thereof and are tuned to individual ones of the frequency components of the modulated wave signal developed in the output circuit of the modulator 3S. These frequency components, as in the case of those developed by the modulator 23 previously discussed, are of relatively low frequency to facilitate their selection by the selectors of units Sli-L33, inclusive. A heterodyne oscillator lid is coupled to the input circuits of the modulators of units 39-43, inclusive, for the purpose of increasing the frequencies of these frequency components to values suitable to provide the required modulation signals.

The output circuits of the selector-modulator units Sil-53, inclusive, include selectors which select the difference-frequency heterodyne components developed in these units and which are respectively coupled to an input circuit of a plurality of modulators i5-49, inclusive. An input circuit of the latter modulators is also coupled to the respective translators Iii-20, inclusive, of

the translator array 1Gb. The output circuits of the modulators l5-$9, inclusive, are respectively coupled to the input circuits of a plurality of intermediate-frequency selectors and amplifiers 54-55, inclusive, which have output circuits coupled in common to the input circuit of an intermediate-frequency amplier 56. Following the latter amplifier, in the order named, are a detector 5l and a low-frequency amplifier 53, the output circuit of which is coupled to the input electrodes of a cathode-ray tube 5S to control the cathode-ray beam thereof.

The locating system includes means responsive to the scanning-control signal of the generator 2l for deflecting the cathode-ray beam of the tube '59 in synchronism with the scanning beam of the translator array lila. This means comprises a scanning oscillator GQ having a synchronizing circuit coupled through a delay network Si to the output circuit of the generator 2l and 6 having an 'output circuit coupled 'to 'a pair of deflecting electrodes 62 provided in the 'cathoderay tube 59.

Considering now the operation O f the locating system just described, the Wave'signal generated by the generator 22 is modulated 1in the balanced modulator 23 with the scanning-control signal of the generator V2l to provide a modulated wave signal having the frequency components 'designated in association with the modulator 23 in Fig. 1. Individual ones of these frequency components are Selected by the selectors of the selector-modulator units 25-29, inclusive, and are raised to higher frequencies in the latter units by heterodyne oscillations supplied by the oscillator B. It is the purpose of unit 2A to increase the frequencies of the modulation-frequency components to values suitable for radiation; hence, 'it is'preferable to select the sumfrequency heterodyne components developed in the output circuits of the units 25429, inclusive, and this is doneby the selectors of the selector-amplifier units 3 l-35, inclusive. These selected components have frequencies indicated in Fig. -1 in association with the latter units and are applied to the translators of the array Illa for radiation therefrom.

It will be seen from inspection of Fig. 1 'that the wave signals applied to the translators ofthe array lila haveindividual difference 'frequencies which increase in order in the frequency spectrum in the order of positioning of the translators in the array la'starting with the end translator l 5. When the translator array lila is excited by 'wave signals in this manner, its directional radiation characteristic is in the nature of a sharply concentrated radiated-signal beam having maximum value in a direction which angularly scans, with at least one major radiation lobe or beam, through an angle of degrees. The reason for this is explained in detail in the cope'nding Lewis application, SerialNo. 507,859, previously mentioned. Very briefly, the wave signals applied to the translators of the array! lla may be considered as equivalen-t to waves having the same Ainstantaneous frequency but relative values of phase angles which vary linearly With time and are proportional to the physical spacings of the translators in the array. These relative phase variations cause the directive radiation characteristic of the array to scan sinusoidallyvvith time. As a result, then, the array of translators Illa angularly scans a predetermined space with a radiated-signal beam.

Due to the physical spacings of the translators of the array Illa and the eifective phase displacements of the wave signals applied to the translators thereof, the radiation field intensity at any radiated-signal reflector may be considered as having substantially zero value except during the small interval of time when the radiated-signal beam is sweeping across Ithe reflector. Consequently, the reflected radiated-signal energy has the frequency of the wave signal applied to the translator I3, with sideband amplitude-modulation components, with the result that the reflected radiated-signal energy also is effectively a carrier wave amplitude-modulated with pulse components.

by anc-ther,

The reflected radiated-signal energy is ated-signal energy received by the array los which are in phase, the balanced modulator 36 derives a modulated wave signal in the manner of the modulator 23 previously discussed and the modulation components of this wave signal are individually selected by the selectors of units 39-43, inclusive, heterodyned to a higher frequency by the action of the heterodyne oscillator 44 and the modulators of units 39-43, inclusive, and are applied as modulation signals individually to the modulators 45-49, inclusive. As explained in the copending Lewis application, Serial No. 507,860, filed concurrently herewith, entitled Radiated-signal receiving system, and assigned to the same assignee as the present application, the

use of modulation signals having related frequencies of this nature has the eiect that predetermined ones of the resulting modulation components developed in the output circuits of the modulators 45-49, inclusive, have additive phase only for one direction of reception by the translators of the array IGb, but this direction angularly and periodically scans a predetermined space. The application to the modulators l5-69, inclusive, of modulation signals having values of frequency, designated in Fig. 1, which are related to the frequencies of the wave signals applied to the translators of the array Ia, ensures that the directive-response characteristic of the array it scans in synchronism with the radiated-signal beam of the array Ilia. This required frequency relationship, which is considered hereinafter in greater detail, is established and maintained in the present locating system by deriving the modulation signals and applied wave signals in common from the frequency components of the scan,l ning-control signal generated by the generator 2 i Hence, any radiated-signal energy reflected by a reector in the scanned space is received by the array I b and components of the reilected radiated-signal energy are caused to be in phase in the output circuits of the modulators i5-e9, inclusive, by selective utilization of the modulation components, as explained. This in-phase energy is selected and amplified by the units Fil-55, inclusive, combined in the common input circuit of the amplifier 56, detected by the detector 5l, and the detection components after amplification by the low-frequency amplifier 5S are applied to the input electrodes of the cathoderay tube 59.

The cathode-ray beam of the tube EQis periodically deflected by oscillations, which may be of saw-toothwave form, generated by the oscillator 6! which is synchronized in operation by the scanning-control signal of the generator 2l applied thereto through the delay network Si.

The cathode-ray beam or tube 59 thus scans in Synchronism with the radiated-signal beam oi' the array lila. It is the purpose of the delay network El so to control the scanning action that the cathode-ray beam of tube E@ initiates a scanning cycle at a moment when the radiated-sig nal beam of the array iEl-.i extends in the direction of alignment of the translators of the array. One rentire trace of the cathode-ray beam thus corresponds to a scanning angle of substantially 180 degrees of the radiated-signal beam and the center of the trace corresponds to the position of the radiated-signal beam normal to the direction of alignment of the translators of the array Illa where the configuration of the beam is sharpest.

As the radiated-signal beam ofthe array les and the directive-response characteristic of the array lb scan the predetermined space in synchronism, a pulse or burst of radiated-signal energy is reflected by the reector each time the radiated-signal beam scans across it. This burst or pulse of radiated-signal energy, after it is received by the array Elib and suitably modulated by the modulators l5-49, inclusivey amplied by the ampliers 5i-55, inclusive, and the ampliiier 55, and detected by the detector 5l, produces a unidirectional potential of periodic pulse wave form of which each pulse thereof corresponds to a pulse or burst of received radiated-signal energy. This derived periodic potential is amplilied by the amplifier 58 and applied to the input electrodes of the cathode-ray tube 59 to modulate the cathode-ray beam thereof, whereby there is produced on the screen of this tube a Spot, the position of which on the trace of tube 59 is indicatiVe of the direction of the radiated-signal reflector from the locating system.

Since a discrete interval of time is required for the energy of the radiated-signal beam of the array los to travel to the radiated-signal reiector and to be reected therefrom to the receiving array ib, a rapid rate of scanning by the arrays of the translator system i0 and the desirability of locating distant reflectors renders advisable the use of the adjustable phase shifter 3l. The latter has the effect of introducing a phase delay between the modulation signals applied to the modulators 1315-49, inclusive, and the wave signals applied to the translators of the rray ma, whereby the directive-response characteristicof the array lb scans in synchronism with the radiated-signal beam of the array Illa, as mentioned, but angularly lags the latter by a selectable value established by adjustment of the phase shifter 32. It may be noted in this regard that adjustments of the phase shifter 31 do not change the position along the trace on tube 59 of any spot produced by received Wave energy, since its position is determined solely by the direction from which the received wave energy arrives at the translator array lh and the distance of the radiated-signal reilector from the translator arrays its and ist, but rather change the intensity oi the spot by causing the array Mib to have maX- imurn response in the direction of arrival of the received wave energy at the moment of arrival thereof, The reasons for this will now be eX- plained with reference to Figs. 1A and 1B. Curve K of Fig. 1A represents the directional radiation characteristic of the translator array its at a selected moment after it has scanned through an angle a from 'the axes X-X of alignment of the translators Ii-l, inclusivepoi the array ma. Assume that the radiated-signal beam has maX- imum intensity in the direction of a radiatedsignal reflector P at this selected moment. Assume further as an initial condition that the reflector P is sufciently close to the translator systems lila and lb that the wave-signal propagation interval required for the radiated energy of the beam to travel from the translator system les to the reflector i3 and back to the translator system wb is negligible. Lastly, assume that the adjustable phase shifter 31 is adjusted to provide zero phase shift therethrough so that curve K also represents the directive characteristie of the receiving array mi). The radiatedsignal energy received by reection from the reiiector P is translated through the receiving system in the manner previously described to produce a spot Y, Fig. 1B, on the trace of tube 5S. As earlier explained, the trace of tube 59 is initiated at the moment when the radiated-signal beam of the array Illa is in the direction of alignment of the translators I-l5, inclusive, or, expressed in another manner, when the angle a has zero value. Further, it was previously explained that the cathode-ray beam of tube 59 scans in synchronism with the scanning of the radiated-signal beam of the array its so that the entire trace of tube 59 represents a 180-degree scanning angle of the radiated-signal beam and may be so labeled as indicated in Fig. 1B. The spot Y thus produced on the trace by the received reflected energy directly provides an indication of the angle a which the direction of the radiated-signal reiiector P forms with the alignment aXes X-X of the arrays ida and leb.

Assume now that the direction of the radiatedsignal reflector P is the same as that first assumed but that the distance of the reiiector P from the arrays les and Ib is much greater so that the wave-signal propagation interval now becomes so large that the radiated-signal beam of the array Illa scan through an additional angle Aa, as indicated by the broken-line curve L of Fig. 1A, before the reflected radiated-signal energy propagates back to the receiving array Ib. If the adjustable phase shifter 3'! has the phase shift iirst assumed, curve L of Fig. 1A also represents the directional response characteristic of the receiving array IEib and it will be apparent that the latter has substantially reduced response for the reflected radiated-signal energy. The position of the spot which the reflected-signal energy would produce on the trace 59 if properly received is indicated in Fig. 1B by the brokenline spot Y. The spot Y Will not be produced, of course, until the adjustable phase shifter 3l' is adjusted to provide suiiicient delay that the receiving array Iiib has maximum response in the direction of the reflector P, as represented by curve K of Fig. 1A, under the assumed conditions. When this occurs, the directive-response characteristic of the receiving array lh lagsv that of the array les by the angle Aa and, the receiving array then having maximum response in the direction of the renector P at a moment of reception of reiiected radiated-signal energy therefrom, the spot Y is produced on the trace of tube 5S. It will be apparent, however, that the position of the spot Y on the trace now is determined both by the scanning angle a and by the distance of the reiiector P from the translator systems lila and Ib. Since the scanning by these arrays varies sinusoidally with time, the angle nu provides a measure of the distance of the reilector P from the arrays ids and ist, as indicated by the distance legend d of Fig. 1B. Consequently, the control knob of the adjustable phase shifter is calibrated terms of distance, thus directly to provide an indication of the distance of the radiated-signal reiiector P from the arrays, and is also calibrated in terms of the angle of phase delay so that for any adjustment of the phase shifter 3l the angle a of the reflector P may be obtained from its indicated position on the trace oi tube 5t by subtracting from the indicated position on the trace the phase shift in degrees provided by the phase shifter 3l.

It will now be apparent that the response of of the system to radiated-signal reflectors is in the nature of response bands, the minimum and maximum distance limits of any such response band varying with the scanning velocity, the adjustment of the phase shifter 3l, and with the Width of the scanning lobe of the receivingl array it. In some applications, it may be desirable continuously and periodically to drive the phase shifter 31 over a predetermined range of its adjustment so that Within each of successive groups of scanning cycles indications of both nearby and distant reectors are provided.

It has heretofore been stated that predetermined ones of the modulation components developed in the output circuits of the modulators #i5-59, inclusive, have additive phase only for one direction of reception by the array Illb. The question regarding which modulation components should be selected by the selectors of units 5I-55, inclusive, to eiiect synchronous scanning of the arrays Illa and lilb Will now be considered with reference to Fig. 1C and a mathematical analysis of the scanning action of these arrays. Consider only the three centrally positioned translators I2, I3 and I4 of the array Illa, as indicated in Fig. 1C, and assume that the vvave signals applied to these translators are given by the respective relations:

e12=E COS (wi-l-wh) l? (l) e13=E cos wit (2) e14=E cos (w1-awt (3) Where wi=2vr(fo+fc) wh=27rfh E -the maximum amplitude of the Wave signals applied to the translators I2, I3 and Ill.

As shown in the aforementioned Lewis application, Serial No. 507,859, the Wave-signal energy received by a distant radiated-signal reflector in a direction a from the axis of alignment of the translators I2, I3 and Ill is:

eszE [1-l-2 cos (wht-l-Z'lra cos a) l cos wit (il) where d=the spacings, assumed equal, of the translators Within each array expressed in arbitrary unit,

l=the wave length of the wave signal applied to the translator I3 expressed in the same unit as d,

E'=lcE, and

c=the attenuation factor of the received Wave signals due to their space propagation.

A method of graphically solving Equation 4 is described and illustrated in the aforementioned Lewis application, Serial No. 507,859, 'and it is there shown that the radiated-signal beam of the array Iila scans a predetermined space at an angular frequency wh, the direction of scanning progressing from the translator having the highest-frequency mave signal applied thereto toward the translator having the lowest-frequency applied Wave signal. Under the conditions above assumed, the direction of scanning by the radiated-signal beam is from the translator I2 toward the translator Ill, or from right to left in Fig. 1C.

Scanning systems of this nature may be said to have a radiated-signal beam or major lobe of radiation for the reason that during a particular short interval of each scanning cycle the radiated Wave signals of the translators all add in phase at a given distant point fixed in space, but have such diiering phases during the remaining portions oi theV scanning cycle that the resultant radiated-signal energy received at the given point is. substantially Zero. At the moment when the radiated-signal beam of the array la thus scans across the remotely situated radiated-signal reflector, the phase coefficient of Equation 4 equates to zero; that is, the sum of wht and 21ra cos a must either equal zero or 21m where n is any integer. The radiated-signal energy of all of the translators of the array Illa is then in additive phase and the radiated-signal energy of the beam reflected by the reflector has the angular frequency w1.

Now assume that the receiver translator array 59h is positioned relatively closely to the transmitter array ma so that the reflector is also remotely situated from the former. The reflected radiated-signal energy arrives at the array IElb from adirection forming the same angle or with the direction of alignment of its translators l1, i3 and IS. Hence, the wave-signal energy received by the translators of the array Illb may be expressed by the respective relations:

e1f1=E cos (wit-|-21ra cos (5) e1s=E" cos wit (6) e19=E cos (wit-21m cos a) (7) where ElfzklEl 7 1=the combined coefficient of radiant-energy reflection of the radiated-signal reflector and attenuation factor due to space propagation.

Equations 5, 6 and 7 are based on the assumption that the time required for wave-signal energy to travel from the array Illa to the reflector and back to the array ill, is negligible. In practice, any variations from this assumption are compensated by the adjustable phase shifter 3l which adds an electrical phase shift corresponding tothe phase shift existing between the radiated and received wave signals due to the'time of transit of the latter through space.

Assume now that there are applied t the modulators 46, all and 138, associated with the respective translators l1, I8 and I9, modulation signals given by the respective relations:

where E0=the amplitude of the modulation signals applied to the modulators 15, il and 48, and w0=21.-(f0-fc) Assume further that the difference-frequency modulation components developed in the output circuits of'the modulators 45, l1 and 48 are selected by the intermediate-frequency selectors of the respective units 52, 53 and 54 and combined in the common input circuit of the intermediatefrequency amplifier 55. It can be shown that the combined difference-frequency components produce an intermediate-frequency wave signal eX- pressed by the relation:

Equation ll can be graphically solved in the manner described and illustrated in the aforementioned Lewis application, Serial No. 507,859. When this is done. it is found that the directiveresponse characteristic of the array lllb scans in the direction from that translator which is associated with the modulator having the lowestfrequency applied modulation signal toward the translator which is associated with the modulator having the highest-frequency applied modulation signal or, under the conditions assumed, from the l2 translator I1 toward the translator I9. This direction of scan-ning is the same as that of the array Illa and, hence, the two arrays have directive characteristics which scan a predetermined space in synchronism.

While only three translators of the arrays Illa and Iilb have been considered in the preceding analysis, it can readily be shown by similar analysis that the same result is obtained when all of the translators of the array are considered.

Under the conditions above assumed, it can readily be shown that if the sum-frequency modulation components were selected Iby the selectors of units 52, 53 and 54 this would have the effect that the directive-response characteristic of the array Ib scans in the opposite direction to that of the array Ia. It will thus be evident that where a higher-frequency modulation signal is applied to the modulator 455 and a lower-frequency modulation signal to the modulator 48, the sumfrequency modulation components must be selected by the selectors of units 52, 53 and 54 to cause the directive-response characteristic of the array |01 to scan in synchronism and in the same sense with the array lila. Selection of the differe-nce-frequency modulation components would, in such case, cause the directive-response characteristic of the array |01, to scan in a direction opposite to that of the array Illa. It is usually preferable that the amplifiers of the units 5I-55, inclusive, be relatively low-frequency amplifiers for reasons well known to one skilled in the art and, hence, that the frequencies of the modulation signals applied to the modulators l5-49, inclusive, be such that the difference-frequency modulation components may be selected and utilized since these components have a frequency much lower than that of the wave signals radiated by the array Illa.

While the heterodyne oscillator 44 of the receiving system is indicated as having a frequency equal to that of the heterodyne oscillator 30 of the transmitting system, this is doneffor purposes of simplicity only and it will be understood that the only requirement regarding the oscillator 44 is that the wave signal generated thereby should have the proper frequency to produce intermediate-frequency wave signals of the frequency to which the amplifiers of units 5I-55, inclusive, and 56 are tuned. Additionally, while the translator system lll is shown as including separate transmitter and receiver arrays lila and Ib, respectively, it will be appare-nt to one skilled in the art that the translators of the array lila may be utilized both as radiating and receiving translators, it being only necessary to provide, for example, transmission lines of suitable length between the output circuits of the selector-amplifier units 3l-35, inclusive, and the translators ||-l5, inclusive, on they one hand, and suitable lengths of transmission lines between the lastmentioned translators `and the input circuits of the receiver modulators. In this event, the transmitter system is operated with pulse modulation, as described in the aforementioned application, Serial No. 507,859.

From the above description 0f the Fig. 1 arrangement, it will Ibe seen that the generators 2| and 22, the balanced modulator 23, and the selector-modulator unit 24 comprise means responsive to the signals of the generator 2| for deriving a plurality of wave signals having individual frequencies spaced in the frequency spectrum in proportion to the physical spacings of individual predetermined ones of the translators of the translating system I0, these Wave signals being 13 equally spacedV in*V the frequency spectrumY where the translators I I-I 5, inclusive, of the translating system are equally spaced in the array lila. Similarly, it will be seen that the generators 2l and 22, the balanced modulator St, the selectormodulator unit 3S, and the modulators li5-9, inclusive, comprise means responsive tothe signals of the generator 2i for modulating the reflected radiated-signal energy individually received by individual predetermined ones of the translators of the translating system IS with individual modulation signals having individual frequencies different from the wave signals applied to the translators of. the array les and spaced in the frequency spectrum in proportion to the physical spacing of the individual translators of the array Ille to cause predetermined ones of the resulting modulation components to have additive phase only for one direction of reception by the translators of the array ills, which direction scans a predetermined space in synchronism with the radiated-signal beam of the array ita. In this connection, it may be noted that the modulation signals are equally spaced in the frequency spectrum where the translators of the array [b have equal physical spacings.

From the foregoing description of the Fig. 1 system, and particularly from Equations 4 and 11 thereof, it will be apparent that the period of scanning or the systems directivity characteristic varies with the fundamental and harmonic frequencies wh and 2am of the signal generated by the scanning-control signal generator 2l. Thus, the period of scanning may easily and readily be varied simply by variation of the frequencies of this generator. Any such adjustments may, of course, require slightcorresponding` readjustments of the tuning oi?y the band-pass selectors of the transmitter units 25-23, inclusive, and of the receiver units 15g-43, inclusive, which may be accomplished if desired by suitable unicontrol tuning means. The configuration of the transmitter scanning beam or major lobe, and particularly the ratio of the amplitudes of the major to minor lobes, varies with the relative amplitudes of the wave signals translated by the transmitter units 3h35, inclusive, and hence may be controlled by relative adjustments of the gains of the ampliers included in the latter units. In similar manner, the coniiguration of the major and minor lobes of the receiver Varies with the relative amplitudes of the modulating signals applied to the receiver modulators LS-9, inclusive, and may be controlled by relative adjustments oi the amplitudes of the signals supplied by the rel ceiver units 39-43, inclusive.

In some applications, it may be desirable to provide a system of the type described in which scanning of a predetermined space is effected in two directions normal to each other. It will be apparent that this may readily be done by the provision of a second system of the type shown in Fig. l and hereinbefore described but with the radiated-signal translators of the former positioned and aligned normal to the translators of the latter system. In this case it is preferable that the additional or second system scan at a different rate than the rst in order that its output signal may be applied to deflecting electrodes additionally provided in the cathode-ray indicating tube normal to those to which the first system is coupled. The resulting scanning pattern is then essentially a raster of parallel scanning lines and received reflected energy of the scanning beam produces on the screen oi the indicating iii) 14 tube intersecting lines normalto each other, the intersection of the lines providing. an indication in two dimensions of the position ofthe reflector.

Fig. 2 schematically represents a complete radiated-signal locating system which is essentially similar to that of Fig. l, similar elements being designated by similar reference numerals and analogous elements by similar reference numerals primed. The system of Fig. 2 differs from that of Fig. 1 in that the translator arrays ia and lb of the translator system Hl each include an even number of radiated-signal translators. These translators may, for example, be vertical dipole antennas horizontallyv aligned and preferably equally spaced in each array. There is the additional difference in the present arrangement that the modulation signals for the modulators of the receiving system are obtained from the output circuits of the transmitter selector-modulator unit 24.

Considering iirst the use of an even numberof translators in each array, as distinguished from the odd number of translators used in the array of the Fig. 1 arrangement, it Will be seen that neither array of the Fig. 2k translator system I0 has a translator which is centrally positioned with relation to all of the translators of the array. However, there is a point in each array which can be considered the central point of` the array and the scanning-control signal of the generator 2l has frequency components, the values` of which are indicated in Fig. 2, related to the spacings of the translators from such central point of the array. The balanced modulator 23 is of the so-called suppressed carrier type wherein the Wave signal of the generator 22 is suppressed in the output circuit of the modulator 23. The use of an additional translator in the transmitter array ia requires, of course, an additional selector-modulator unit 63 and selector-amplifier unit 54 for deriving the wave signal which is applied to the radiated-signal translator 65.

In regard to the arrangement utilized in Fig. 2 for supplying modulation signals to the modulators of the receiving system, the sum-frequency heterodyne components developed in the output circuit of the selector-modulators of unit 24 are selected and applied to the following selector-amplier units :iV-35', inclusive, and G4, as in the Fig. 1 arrangement. The diiTerence-frequency heterodyne components developed in the output circuits of the selector-modulators of unit 24 have the correct values of frequency to be used as modulation signals for the modulators 3F-49', inclusive, and a modulator 6'! required for a sixth radiated-signal translator 65 used in the receiver array lllb. To effect synchronous scanning of the directional-radiation characteristics of the arrays Ia. and Mlb, the sum-frequency heterodyne components are applied to the radiatedsignal translators of the array la in the order which the translators have in this array and the diiTerence-frequency modulation components are applied to the modulators l5-49, inclusive, and 61 in the order in which their associated translators occupy in the array l Qb in corresponding relation to the translators of the array la, as shown in the drawings. This method of obtaining the modulation signals for the receiving system has the advantage that it appreciably simplies the locator system since it dispenses with the phase shifter 3?, the balanced modulator 36, and the selector-modulator unit 38 required in the Fig, 1 arrangement. There is a limitation, however,

that high rates of scanning may not be possible in certain applications since the present arrangement has no means for angularly displacing the directive-response characteristic of the array |b from that of the array 10's to compensate for the time required for radiated-signal energy to travel from the array lila to the radiated-signal reflectorrand back to the array Ilb.

An additional intermediate-frequency selector and amplier unit 68 is provided to couple the output circuit of the modulatol` unit Si' to the common input circuit of the intermediate-frequency amplifier 56.

The operation of the Fig. 2 locating system is essentially similar to that of Fig. 1 except for the frequencies of the derived Wave signals, the translated Wave signals, and the modulation signals applied to the modulators of the receiving system, these several signals having the individual frequencies designated in Fig. 2. In this regard, it will be noted that the scanning-control signals of the generator 2| have frequency components proportional to the spacing of the translators of the array IUa and lb from a point in each array common to all of the translators thereof, which for the frequencies indicated in Fig. 2 is the point at the center of each array. The reason for this choice of frequency components is considered in greater detail in copending applications, Serial Nos. 507,859 and 507,860, previously mentioned. The frequency designations of Fig. 2 are suitable for a system in which the translators of the arrays la and ib have equal spacings within each array and this spacing in the array l'b is the same as that in the array 's. Aside from the wave-signal and modulation-signal frequencies, the operation of the Fig. 2 locating system is otherwise the same as that of Fig. 1 and the described operation will therefore not be repeated.

Fig. 3 schematically represents a portion of a locating system essentially similar to that of Fig. 1, similar elements being designated by similar Vreference numerals and analogous elements by similar reference numerals double primed, except that the Fig, 1 translator lg, its associated modulator 41 and amplifier 453, and the selector-modulator il of the unit 38 have been omitted in the Fig. 3 arrangement, as indicated by the broken lines. The array Ilia of the present arrangement thus has five translators, Whereas the array has only four translators with the translators ii and i9 thereof spaced by twice the spacing of the pairs of translators I6 and l'I or l 9 and 20. Additionally, and for a reason presently to be explained, amplier of unit 33 in the present arrangement preferably has a gain 2.25 times that of the amplifiers in the units `3 l, 32, 34 and 35.

The operation of the Fig. 3 locating system is essentially similar to that of Fig. 1, differing only therefrom in that minor or spurious radiation lobes characteristic of the array 50a intervene between minor or undesired lobes of the directional-response characteristic of the array lb.

16` Equation 4 above used in connection with the array lila of the Fig. 1 arrangement, is given by the relation:

2Ycos 2 (wht-i-21ra cos C01 cos wir (l2) The directional-radiation characteristic of the array a of the Fig. 3 arrangement is shown by the solid-line curves A, B and C of Fig. 4 at three selected intervals during a scanning cycle; namely, at intervals wht equal to 1r, 31r/2, and 21T. Curves A, B and C were obtained by graphical solution of Equation 12 in the manner described and illustrated in the aforementioned application, Serial No. 507,859.

The intermediate-frequency Wave signal developed in the common output circuit of the selector-amplifier units 5l, 52, 5d and 55 of the receiving system can be shown, by an analysis similar to that employed above in connection with the receiving system of the Fig. 1 arrangement, to be one expressed by the relation:

.2 cos 2 wht+27ra cos o0] cos (w1-wo) t 13) Equation 13 can be graphically solved, in the manner of the graphical solution of Equation 12, to obtain the directional-response characteristic of the receiver array Ib of the Fig. 3 arrangement. The broken-line curves D, E and F of Fig. 4 were obtained in this fashion and represent this characteristic at selected intervals during a scanning cycle corresponding to values of wht equal to w, livr/2, and 2W, respectively.

It will be apparent from inspection of curves A-F, inclusive, that when a minor or spurious lobe of radiation of the array its causes an undesired reflection from a radiated-signal reector, the corresponding receiver-system directionalresponse characteristic is substantially zero. Thus, the Fig. 3 locating system has the important advantage that indications are provided of only those radiated-signal reflectors which reflect radiated-signal energy of the major radiation lobe or scanning beam of the array its. The operation of the Fig. 3 arrangement is other- Wise essentially similar to that of Fig, 1 and the described operation will therefore not be repeated.

The aforementioned copending applications, Serial Nos. 507,859 and 507,860 disclose respective transmitting and receiving systems having directivity characteristics which scan a predetermined space in tWo dimensions normal to each other. From the above description of the present invention, it Will be apparent that a locating system capable of scanning space in tWo directions may be readily eiected by utilizing twodirectional scanning transmitters and receivers of the types disclosed in the aforementioned copending applications. This type of locating system has numerous advantages which will be apparent to one skilled in the art.

The pulse-modulation types of operation described in the aforementioned copending application, Serial No. 507,859, are equally applicable to the locating system of the present invention. The receiver of the present system in such case may be either operated with constant sensitivity or the pulse-modulation potentials, for example, may be applied to a gain control circuit of the receiver, as to such circuit of the amplifier 58, suitably to control its sensitivity in a periodic manner.

While there have been described what are at present considered t0 be the preferred embodi- 17 ments of this invention, it will be obvious to those skilled in the art that various changes and modiflcations may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A system for locating a radiated-signal reiiector comprising, a radiated-signal translating system including a plurality of spaced signal wave-signal supply means for applying wave signals to at least one of said translators and wave signals of a different frequency to another of said translators to provide a radiatedsignal translating system which angularly scans a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflector in said space and radiatedsignal energy of said beam is reflected therefrom, modulator means for modulating the reflected radiated-signal energy received by one of said translators with a modulation signal having a predetermined frequency different from the wave signal applied to said rst-mentioned one translator and for modulating the reflected radiatedsignal energy received by another of said translators with a modulation signal having with respect to the wave signal applied to said firstmentioned other translator a predetermined frequency difference such that predetermined ones of the resulting modulation components have additive phase only for one direction of reception by said translators which direction scans, said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

2. A system for locating a radiated-signal reilector comprising, a radiated-signal translating Vsystem including a plurality of spaced signal translators, wave-signal supply means for applying wave signals to at least one of said translators and wave signals of a different frequency to another of Said translators to provide a radiated-signal translating system which angularly scans a predetermined space with a radiatedsignal beam, whereby said beam scans across any radiated-signal reflector in' said space and radiated-signal energy of said beam is reflected therefrom, modulator means for modulating' the reflected radiated-signal energy received by one of said translators with a modulation signal having a predetermined frequency difference from the wave signal applied to said first-mentioned one translator and for modulating the reflected radiated-signal energy received by another -of said translators with a modulation signal having with respect to the wave signal applied to said firstmentioned other translator a frequency dilerence not less than said predetermined frequency difference, whereby predetermined ones of the resulting modulation components have additive phase only for one direction of reception by said translators which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

3. A system for locating a radiated-signal reflector comprising, a radiated-signal translating system including a plurality of spaced signal ing wave signals to at least one of said translators and wave signals of a different frequency to another of said translators to provide a. radiatedsignal translatingsystem which angularly scans a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflector in said space and radiated-signal energy of said beam is reflected therefrom, modulator means for modulating the re- -flected radiated-signal energy received by one of said translators with a modulation signal having a predetermined frequency difference from the wave signal applied to said first-mentioned one translator and for modulating the reflected radiated-signal energy received by another of said translators with a modulation signal having with respec't to the wave signal applied to said iirstmentioned other translator a frequency difference which is greater than said predetermined frequency difference by twice the frequency difference between said applied wave signals, whereby predetermined ones of the resulting modulation components have additive phase only for one direction of reception by said translators which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

tl. A Ysystem for locating a radiated-signal reilector comprising, a radiated-signal translating system including a plurality of spaced signal translators, wave-signal supply means for applying wave signals to at least one of said translators and wave signals having an incremental frequency difference therefrom to another of said translators to provide a radiated-signal translating system which angularly scans a predetermined space with a radiated-signal beam, whereby said beam scans across any radiatedsignal reflector in said space and radiated-signal energy of said beam is reflected therefrom, modulator means for modulating the reflected radiated-signal energy received by one of said translators with a modulation signal having a predetermined frequency difference from the wave signal applied to said first-mentioned one translator and for modulating the reflected radiatedsignal energy received by another of said translators with a modulation signal h'aving with relation to said first-mentioned modulation signal said first-mentioned frequency difference, whereby predetermined ones of the resulting modulation components have additive phase only for one direction of reception by said translators which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

5. A system for locating a radiated-signal reflector comprising, a radiated-signal translating system including a plurality of spaced signal translators, a source of scanning-control signals having frequency components related to the spacing of said signal translators, means responsive to the signals of said source for deriving a plurality of wave signals of individual different frequencies and for applying said derived wave signals individually to translators of said translating system to causesaid translators angularly to f scan `a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflector in said space and radiated-signal energy of said beam is reflected therefrom, means responsive to the signals of said source for modulating the reflected radiatedsignal energy individually received by translators of said translating system with individual modulation signalsY having individual different frequencies related to the frequencies of the Wave signals applied to said Erst-mentioned translators to cause predetermined ones of the resulting modulation components to have additive phase only for one direction of reception by said last-named translators which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reilector from said system.

6. A system for locating a radiated-signal reector comprising, a radiated-signal translating system including a plurality of spaced signal translators, a source of scanning-control signals having frequency components proportional to the spacing of said translators from at least one common reference point, means responsive to the signals of said source for deriving a plurality of wave signals of individual different frequencies and for applying said derived wave signals individually to translators of said translating system to cause said translators angularly to scan a predetermined space with a radiated-signal beam, whereby said beam scans across any radiatedsignal reector in said space and radiated-signal energy of said beam is reflected therefrom, means responsive to the signals of said source for modu-l lating the reected radiated-signal energy individually received by Jtranslators of said translating system with individual modulation signals having individual different frequencies related to the frequencies of the wave signals applied to said first-mentioned translators to cause predetermined ones of the resulting modulation components to haveadditive phase only for one direction of reception by said last-named translators which direction scans said predetermined space in Ysynchroni'sm with said radiated-signal beam, and means for combining and utilizing said pre- .determinedmodulation components to indicate .the direction of said reilector from said system.

'7. A systemfor locating a radiated-signal reector comprising, a radiated-signal,translating system vincluding a plurality of spaced signal translators, a source of scanning-control signals having frequency components related to thespacing of said signal translators, means responsive to the signals of said source for deriving a plurality of wave signals of individual different frequencies and for applying said derived wave signals individually to translators of said translating system to cause said translators angularly to scan a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflectorin said space and radiatedsignal energy of said beam is reflected therefrom, adjustable phase-control means coupled to said source for translating scanning-control signals havingselectable values Yof phase relative to the signals of said source, means responsive to scanning-control signals translated by said phasecontrol means for modulating thereflected radiated-signal energy: individually received by translators-of said translating system with individual modulation signals having individual different frequencies related to the frequencies of the wave signals applied to said first-mentioned translators to cause predetermined ones of the resulting modulation components to have additive phase only for one direction of reception by said flast-named,translators which direction scans said Vpredetermined'space*in synchronisni WithY said radiated-signal beam butV angularly Vdisplaced therefrom, by a selectable value established by adjustment of said phase-control means, and means for combining and'utilizingv said'predetermined modulation components to indicate the direction of said reflector from said system.V

8. A system for locating a radiated-signal reflector comprising, a radiated-signal translating system including a plurality of spaced signal translators, a source of scanning-control signals having frequency components related to the spacing of said signal translators, means responsive to the signals of said source for deriving a plurality of wave signals of individual different frequencies, means for heterodyning said wave signals to higher frequencies and for selecting and applying the sum-frequency heterodyne components individually to translators of said translating system to cause said translators angularly to scan a predetermined space with a radiatedsignal beam, whereby said beam scans across any radiated-signal reilector in said space and radiated-signal energy of said beam is reflected therefrom, means for selecting the difference-frequency heterodyne components and for modulat- Y ing the reflected radiated-signal energy individu.- ally received by translators of said translating system with individual ones of said last-named components to cause predetermined onesof the resulting modulation components to have additive phase only for one direction o-f reception by said last-named translators which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

9. A system for locating a radiated-signal reiiector comprising, a radiated-signal translating system including a plurality of spaced signal translators, a source of scanning-control signals having frequency components related to the spacing of said signal translators, means responsive 'to the signals of said source for deriving a plurality of wave signals having individual frequencies spaced in the frequency spectrum in proportion tothe physical spacing of individual predetermined ones of said translators and for applying said derived Wave signals individually to said vindividual predetermined translators to cause said last-named translators angularly to scan a predetermined space with a radiated-signal beam, `whereby said beam scans acrossV any radiatedsignal reflector'in said space andradiated-signal energy'of said beam is reilected therefrom, means responsive to the signals of said source for modulating the reflected radiated-signal energy individually received by individual predetermined ones of said translators with individual modulation signals having individual frequencies different from said derivedyvave signals and spaced in the frequency spectrum in proportion to the physical spacing of said last-named individual predetermined translators to cause predetermined'ones of the resulting modulation components to have additive phase only for one direction of reception by said last-named translators'which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining Vand'utilizing said predetermined modulation components to indicate the direction of said reflector from said system. Y

10. A system for locating a radiated-signal re- 2l fiector comprising, a radiated-signal translating system including a plurality of equally spaced signal translators, a source of scanning-control signals having frequency components related to the spacing of said signal translators, means responsive to the signals of said source for deriving a plurality of Wave signals having individual frequencies equally spaced in the frequency spectrum and for applying said derived wave signals individually to translators of said translating system to cause said translators angularly to scan a predetermined space with a radiated-signal beam, whereby said beam scans across any radiatedsignal reflector in said space and radiated-signal energy of said beam is reflected therefrom, means responsive to the signals of said source for modulating the reflected radiated-signal energy individually received by translators of said translating system with individual modulation signals having individual frequencies different from said derived wave signals and equally spaced in the frequency spectrum to cause predetermined ones of the resulting modulation components to have additive phase only for one direction of reception by said last-named translators which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

11. A system for locating a radiated-signal reector comprising, a radiated-signal translating system including a plurality of spaced signal translators grouped inte at least two translator arrays, a source of scanning-control signals having frequency components related te the spacing of said signal translators, means responsive to the signals of said source for deriving a plurality of wave signals of individual different frequencies and for applying said derived wave signals individually to the translators of one of said arrays to cause said one array angularly to scan a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflector in said space and radiated-signal energy of said beam is reflected therefrom, means responsive to the signals of said source for modulating the reflected radiated-signal energy individually received by the translators of another of said arrays with individual modulation signals having individual different frequencies related to the frequencies of the wave signals applied to said one array to cause predetermined ones of the resulting modulation components to have additive phase only for one direction of reception by said other array which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components t indicate the direction of said reflector from said system.

12. A system for locating a radiated-signal reector comprising, a radiated-signal translating system including a plurality of spaced signal translators grouped into at least two translator arrays with the number of translators in one array differing by an odd number from that in another array, a source of scanning-control signals having frequency components proportional to the spacing of the translators in each array from a, point common to said each array, means responsive to the signals of said source for deriving a plurality of wave signals having individual frequencies spaced in the frequency spectrum in proportion to the physical spacing of the translators of one of said arrays and for applying said derived wave signals individually to the translators of said one array to cause said one array angularly to scan a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflector in said space and radiated-signal energy of said beam is reflected therefrom, means responsive to the signals of said source for modulating the reflected radiated-signal energy individually received by the translators of another of said arrays with individual modulation signals having individual frequencies different from said derived wave signals and spaced in the frequency spectrum in proportion to the physical spacing of the translators of said other array to cause predetermined ones of the resultant modulation components to have additive phase only for one direction of reception by said other array which direction scans said predetermined space in synchronism with said radiated-signal beam, and means for combining and utilizing said predetermined modulation components to indicate the direction of said reflector from said system.

13. A system for locating a radiated-signal refiector comprising, a radiated-signal translating system including a plurality of spaced signal translators, a source of scanning-control signals having frequency components related to the spacing of said signal translators, means responsive to the signals of said source for deriving a plurality of wave signals of individual different frequencies and for applying said derived wave signals individually to translators of said translating system to cause said translators angularly to scan a predetermined space with a radiated-signal beam, whereby said beam scans across any radiated-signal reflector in said space and radiated-signal energy of said beam is reflected therefrom, means responsive to the signals of said source for modulating the reflected radiated-signal energy individually received by translators of said translating system with individual modulation signals having individual dierent frequencies related to the frequencies of the wave signals applied to said first-mentioned translators to cause predetermined ones of the resulting modulation components to have additive phase only for one direction of reception by said last-named translators which direction scans said predetermined space in synchronism With said radiatedsignal beam, a cathode-ray tube, means responsive to said scanning-control signal for deflecting the cathode-ray beam of said tube in synchronism with said scanning beam, and means for combining and utilizing said predetermined modulation components to control the cathode-ray beam of said tube to indicate the direction of said reector from said system.

HAROLD M. LEWIS. 

